This invention relates to a method of hot-melt sizing of warps for weaving.
Sizing is important as a preparatory process for weaving in order to obtain good weaving performance from yarns by providing them tenacity and cohesiveness. There are many sizing methods including use of conventional sizing agents, oiling agents and hot-melt sizing agents. The present invention relates in particular to methods which use a hot-melt sizing agent.
According to conventional "sizing" methods, warps are dipped in an aqueous solution or water dispersant of a sizing agent, squeezed by press rollers and dried. Methods of this conventional type are disadvantageous, however, because much energy, time and space are required for the drying process. In some areas of fabric industries, there have been sizing methods without using any sizing agent or by using an oiling agent instead of a sizing agent. These methods, however, are usable only in very limited areas and not as universally applicable as methods with conventional sizing agents.
In view of the above, a method of using a hot-melt sizing agent has been considered as a new method of sizing (U.S. Pat. No. 3,466,717). According to this method, a molten sizing agent (a hot-melt sizing agent) is applied to warps by a roller touch method and is thereafter solidified Although many hot-melt sizing agents have been proposed (U.S. Pat. Nos. 4,136,069, 4,253,840 and 4,401,782 and Japanese Patent Publications Tokkai 50-42190, 50-157496 and 55-142773), melt Viscosity of these sizing agents is too high. These sizing agents, therefore, cannot be uniformly attached to warps or penetrate sufficiently into the interior of warps if they are merely melted by heating and applied to warps. As a result, neither yarn tenacity nor cohesiveness can be attained as expected and the yarns themselves tend to become damaged by tackiness of the applied sizing agent. Although it has been considered in view of the above to reduce the melt viscosity of hot-melt sizing agent (U.S. Pat. No. 4,459,129 and Japanese Patent Publication Tokko 48-23996), this makes it difficult for the sizing agent to solidify and a special forced cooler becomes necessary if it is desired to speed up the sizing process. Even with such a forced cooler, yarns tend to become fixed among themselves (or the so-called "blocking") because the sizing agent does not solidify completely.